Subsurface pumping unit



Jan. 21, 1964 c. l.. ENGLISH suBsuRFAoE PUMPING UNIT 2 Sheets-Sheet 1 Filed Feb. 12, 1962 INVENTOI'?. v CHARLES L. @vac/5H ,47' OPA/LYS d. 245066, fa H023? HNr/aSMwd/Vo 3,ll8,382 Patented aan. 21, i9s4 ICC 3,118,382 SUBSURFACE PUMPING UNIT Charles L. English, 2204 E. 25th Place, Tulsa, Okla. Filed Feb. 12, 1962, Ser. No. 172,504 9 Claims. (Cl. 10S-46) This invention relates 'generally to improvements in subsurface pumps utilized in oil wells and the like, and more particularly, but not by way of limitation, relates to fluid operated subsurface pumping units.

Subsurface fluid operated pumping units have been known in the oil producing industry for many years. A complete pumping unit comprises a fluid operated motor and a reciprocating type pump connected in tandem relation. The entire pumping unit is of suciently small diameter as to be lowered through the wellbore to the producing formation. Operation of this type pumping unit is accomplished by pumping power fluid, which is normally clean oil, under relatively high pressure downwardly to the lluid operated motor of the pump unit. The high pressure power fluid operates the motor which reciprocates the pump which pumps both the well fluid and the exhaust fluid from the motor upwardly to the well head. Therefore, it will be evident that at least two separate fluid passagev/ays are required, one for power fluid which is pumped downwardly to the `fluid operated motor, and another for transporting the well fluids and the exhaust fluid from the motor back to the wellhead.

Several different systems have been devised in the art for providing the dual passageways from the wcllhead to the pumping unit. One of the first, and most common, is referred to as the insert type pumping unit. ln the insert type unit, the pumping -unit is lowered through the casing string on the end of a string of tubing. Power fluid can then be pumped downwardly through the tubing string to operate the fluid motor, and the well fluids and exhaust power fluid may be pumped upwardly through the annulus between the tubing string and the casing string. Another type of pumping unit is referred to as the free type unit. The free type pumping unit is provided with suitable annular cups of a size such that the pumping unit can literally be pumped downwardly and upwardly through a string of tubing to and from a pump cavity disposed in the tubing string at the producing formation. The pump cavity is also in fluid communication with another, usually smaller, string of tubing extending to the wellhead. Power fluid may then be pumped downwardly through the first string of tubing in which the pu-mping unit is located to operate the pumping unit. The pressure of the power fluid will also retain the pumping unit seated in the pump cavity. The well fluids, together with the exhausted power fluid from the uid motor, are pumped from the well cavity upwardly through the smaller string of tubing to the wellhead.

These types of subsurface pumping units operate very satisfactorily, but have one serious disadvantage which results in a reduction in operating efficiency. For any particular power fluid pressure selected to operate the fluid motor, the horsepower output of the motor is dependent to a very large extent upon the available hydraulic working area of the fluid motor piston and upon the pressure of the fluid in the exhaust passageway leading back to the wellhead. ln most cases, the combined volume of well fluids and exhaust power fluids being pumped back to the well head will be approximately twice the volume of the lpower fluid being pumped downwardly to operate the fluid motor. However, in both the free type and insert type pumping units referred, the power fluid is pumped downwardly through the larger passageway of the insert tubing string or the tubing string through which the pumping unit is pumped as the case may be. Therefore, in almost all cases, the cross sectional area of the passageway for the power fluid is greater than the cross sectional area of the passageway for transporting the combined =we1l lluids and motor exhaust fluid back to the wellhead. In order to force the double volume of fluid through the smaller fluid passageway, a much greater pressure must ybe generated at the pumping unit, so that the total pressure in the pump unit is equal to the Static pressure head of a volume of fluid extending to the wellhead, plus the pressure required to overcome the frictional resistance to pumping the :fluids upwardly through the small dia-meter tubing string. This pressure is the exhaust pressure against which the fluid motor must operate. As the exhaust liuid pressure increases, the horsepower output of the fluid motor for any given power fluid pressure decreases. However, in order to increase the cross sectional area of the passageway for transmitting the combined well fluids and exhaust fluid to a well surface, the diameter of the tubing string must be reduced, which in turn results in a reduction in diameter of the pump unit and a corresponding decrease in the effective working area of the fluid motor piston.

The problem of providing a passageway for the cornbined well fluids and exhaust fluids of greater cross sectional area than that of the passageway for the power lluid was partially solved by the advent of the so-called reverse flow7 type pumping unit. yin the reverse flow, insert type pumping unit, the pumping unit is connected to the lower end of a relatively large tubing string, and a considerably smaller tubing string is connected to deliver power fluid to the fluid motor. Both tubing strings, together with the pumping unit, are then lowered into the casing string. lliower fluid may then be pumped downwardly through the small tubing string, and the combined well fluids and exhausted power fluids pumped upwardly through the larger tubing string. However, since it is virtually essential that the fluid motor be located above the pump, the diameter of the fluid motor, and therefore the effective working area of the motor piston, must be reduced sufliciently to provide a passageway for the Well fluids pumped by the pump unit. Reverse flow free type pumping units have also been devised wherein the pump Iunit is pumped downwardly through, a relatively large string of tubing to a pump cavity and then locked in the pump cavity, ither by a mechanical or a hydraulic latching mechanism. This type pumping unit and pump cavity is typified by the construction disclosed and claimed in US. Patent No. 2,988,005, issued June 13, 1961, and entitled Subsurface Hydraulic Pump Assembly With Reverse Flow. in that type unit, the power fluid is pumped downwardly through a small tubing string to the pump cavity and then into the fluid motor of the pump unit, and the combined exhaust fluid and well fluids pass upwardly through the larger tubing string. However, the free type reverse flow pumping unit is also subject to the objection that the effective diameter of the fluid motor must be antenna reduced in order to pass the well liuids from the pump around the fluid motor.

Therefore, it is contemplated by the present invention to provide a novel pump unit which, by reason of its novel construction, is particularly adapted for use in a reverse flow type arrangement, and may be utilized equally as well as a free type pump or as an insert type pump. Generally speaking, the present invention contemplates a pumping unit wherein the well lluids are pumped upwardly through the piston member of the fluid motor to the interior of the larger string of tubing so that the motor piston may have a maximum diameter. The exhaust fluid from the lluid motor is also preferably introduced to the iluid passageway means within the piston member. It is further contemplated by this invention to provide a novel main valve operatively positioned in the motor piston member and having a longitudinally extending passageway means therethrough for passing the well fluids from the pump unit and for controlling the eX- haust fluid from the fluid motor. It is still further contemplated by this invention to provide a novel pilot valve assembly for shifting the main valve and thereby causing reciprocation of the fluid motor piston.

Therefore, it is an important object of the present invention to provide an improved subsurface pumping unit of the reverse flow type having an increased efficiency.

Another important object of the present invention is to provide a pump unit of the type described having a novel three-way valve in the fluid motor piston head which increases the operating elliciencies of the iluid motor.

Still another object of the present invention is to provide a novel pilot valve assembly for shifting the main valve which is of simple and economical construction.

Many additional objects and advantages of the present invention will be evident from the following detailed description and drawings, wherein:

FIG. l is a longitudinal sectional view of the fluid motor of a subsurface pump unit constructed in accordance with the present invention;

FIG. 2 is a longitudinal sectional view of a pump which taken in combination with the fluid motor of FIG. 1, constitutes a novel pumping unit constructed in accordance with the present invention;

FIG. 3 is a cross sectional view taken substantially on lines 3-3 of FIG. l;

FIG. 4 is a cross sectional view taken substantially on lines 4-4 of FIG. l;

FIG. 5 is a cross sectional view taken substantially on lines 5 5 of FIG. 1;

FIG. 6 is a longitudinal sectional view taken substantially on lines 6 6 of FIG. 3, but showing only a portion of the piston member of the fluid motor;

FIG. 7 is a somewhat schematic longitudinal sectional view of the piston member of the fluid motor of FIG. 1 showing the valve members in position to cause a downstroke of the piston member;

FIG. 8 is a partial longitudinal sectional view similar to FIG. 7, lbut showing the main valve member in position to cause an upstroke of the piston member;

FIGS. 9, 10 and 1l are partial longitudinal sectional views similar to FIG. 7 showing the pilot valve assembly in various positions, and serve to illustrate the operation of the pilot valve assembly constructed in accordance with the present invention.

Referring now to the drawings, a pumping unit constructed in accordance with the present invention is indicated generally by the reference numeral 1S and comprises that structure shown in FIGS. l and 2. The pumping unit is comprised of a fluid motor, indicated generally by the reference numeral 16, and shown in FIG. l, and a fluid pump, indicated generally by the reference numeral 18 and shown in FIG. 2. The fluid motor 16 is comprised of a motor cylinder 20 having a motor piston 22 reciprocally disposed therein. The motor cylinder 20 i is comprised of an upper packing housing 24, a tubular cylinder sleeve 26 which is connected to the packing housing 24 by a threaded coupling 27, and a lower packing housing 28 which is connected to the sleeve 26 by a threaded coupling 29.

The motor piston member 22 is comprised of three major parts, a piston body 30, about which a plurality of conventional piston rings 32 are positioned for providing peripheral sealing engagement with the cylinder sleeve 26, an insert member 32, and a retainer plug 34, which is threaded into the piston body 30 by a threaded coupling 36 and retains the insert member 32 in place. An upper tubular piston rod 38 having an exhaust fluid passageway 40 therethrough is connected to the retainer plug 34 by threaded coupling 42. The tubular piston rod 38 extends through the upper packing housing 24 and a bushing 44 `which is threaded into the packing housing 24, compresses an annular packing 46 into peripheral sealing engagement with the tubular piston rod 38 in the conventional manner. A tubular connecting rod 48 having a pump fluid passageway 50 therethrough is connected to the piston ybody 30 by a threaded coupling 52 and extends through the lower packing housing 28. A bushing 54 (see FIG, 2) is threaded into the lower packing housing 28 and compresses an annular body of packing material 56 into peripheral sealing engagement with the connecting rod 48 in the conventional manner.

At this point it should be noted that the diameter and therefore the area, of the connecting rod 48 is greater than the diameter, and therefore the area, of the piston rod 38. The motor piston member 22 is therefore a differential area piston in that the effective hydraulic working area of the upper face is greater than the effective working area of the lower face, by an area equal to the difference between the areas of the rods 48 and 38.

The fluid pump 18 (see FIG. 2) is comprised of a pump cylinder member, indicated generally by the reference numeral 58, and a pump piston member, indicated generally by the reference numeral 60. The pump cylinder member 58 is formed by the lower packing housing 28 of the fluid motor 16, a pump cylinder sleeve 62 which is connected to the lower packing housing 28 by a threaded coupling 64, and a standing valve assembly, indicated generally by the reference numeral 66, which is connected to the lower end of the pump cylinder sleeve 62 by threaded coupling 68. The standing valve assembly 66 may be any conventional downwardly closing check valve assembly, and may comprise a body 70 having a fluid passageway 72 extending vertically therethrough. A valve body 74 is disposed in the fluid passageway and has a stem 76 which is reciprocally retained within a guide spider 78. The valve body 74 is provided with a surface adapted to mate with the seat 80 to prevent downward flow of fluid through the passageway 72.

The pump piston member 60 is connected to thc lower end of the connecting rod by a threaded coupiing $2, and has a fluid passageway 84 therethrough which is in fluid communication with the pump Huid passageway 50 in the connecting red 45. A plurality of bores form a lluitl passageway means S6 which is also in continuous fluid communication with the passageway L in the connecting rod 43. A downwardly closing traveling valve 88 is disposed in the fluid passageway 4 to block the downward flow of uid therethrough. The traveling valve 88 has a stem which is retained with a spider guide 92 and seats on an annular sealing surface 93 formed in the body of .ne pump piston 69.

Referring once again to FIG. l, and to the motor piston member 22, a longitudinally extending exhaust fluid passageway means for providing iluid communication bctween the passageway 5G in the connecting rod 4ta' and the passageway 4i? in the piston rod 33 is comprised of an 0"" bore i in the piston body 39, a longitudinaliy extc ng passageway 96 in a main valve member 9S, an

.et bore 166 in the insert 32, and o. bore 292 in the plug insert 34. The main valve member 98 is reciprocally disposed in a main valve cavity, indicated generally by the reference numeral 104.

The main valve member 98 is a differential area, hydraulically shifted valve. The main valve member 98 has three portions, a lower portion 106, an upper portion 108 and a middle portion 110 which are received in sliding, peripheral sealing engagement within a main valve cavity 104 presently to be described. The diameter of the upper portion 108 is greater than that of the lower portion 106, but less than the diameter of the middle portion 110. For convenience of discussion only, the diameters of the three portions may be considered as selected so that the cross sectional area of the upper portion 108 exceeds the cross sectional area of the lower portion 106 by some unit area, and the cross sectional area of the middle portion 110 exceeds the cross sectional area of the upper portion 108 by the same unit area. The main valve member 98 also has an annular groove 112 positioned between the upper and middle portions 108 and 110, and an annular hydraulic control working surface 114 between the middle and lower portions 110 and 106. The hydraulic working area of the surface 114 is equal to the difference between the cross sectional areas of the middle portion 110 and the lower portion 106, which is then equal to two unit areas. An annular control fluid chamber 116 is formed around the main valve cavity 104 and is so constructed as to insure access of control fluid to the entire control surface 114. Four radially extending bores 120 provide uid communication between the longitudinally extending passageway 96 and an annular groove 122 for purposes which will hereafter be evident.

A power uid passageway means for introducing power uid to the interior of the motor cylinder member 20 is comprised of an internally threaded bore 124 in the side of the lower packing housing 28, which is in uid cornmunication with an annular reamed portion 126 of a bore 128 which receives the connecting rod 48. The internally threaded bore 124 is provided for connection to a relatively small tubing string extending to a hydraulic power pump at the wellhead. A second power uid passageway means for supplying power fluid to the main valve cavity 104 is comprised of four bores 130 which extend from the lower end of the motor piston body 30 and intersect an annular passageway 132 which in turn is in iiuid communication with the main valve cavity 104. The four bores 130 may be seen in longitudinal section in FIGS. 6 and 8, and may be seen in the cross sectional views of FIGS. 3, 4 and 5. Therefore, it will be noted that power fluid is continually applied to the lower face of the motor piston member 22 through the passageway means 124, 126, and 128, and to the main valve cavity 104 through the passageway means 130 and 132.

A fluid passageway means for providing fluid communication between the main valve cavity 104 and the interior of the cylinder member 20 above the piston member 22, for applying hydraulic uid pressure to the upper face of the piston member, is comprised of an annular groove 134, which may be formed in the walls of the main Valve cavity 104, three radial bores 136, and the annular passageway 138 formed between the piston member body 30 and the cylinder sleeve 26. A pair of grooves 140, as seen in FIG. 4, may be provided to assist in transmitting fluid uniformly to the annular passageway 138. A fluid passageway means is also provided in the-present invention for establishing fluid communication between the main valve cavity 104 and the exhaust passageway or port 40.- In the embodiment of the present invention being described and illustrated, this passageway means comprises the annular groove 122 and the bores 120 in the main valve member 98, previously described, and the passageway means 96, 100 and 102. l

It will be noted that the main valve member 98 is so dimensioned that when the shoulder formed by the control working surface 114 abuts the face of the control chamber 116, such that the valve member 98 will be in the lower position shown in FIG. l, the annular groove 112 will register with both of the annular passageways 132 and 134, while the annular groove bores will be closed by the valve cavity 104. High pressure power fluid will then be directed from the annular passageway 132 to the interior of the motor cylinder sleeve 26 above the motor piston member 22. Alternatively, when the main valve member 98 is shifted to the up position, with the upper end thereof abutting the shoulder 142, as shown in FIG. 8, the annular groove 112 will register only with the annular passageway 132, and the annular passageway 122 will register with the annular passageway 134. The fluid within the motor cylinder sleeve 26 will then be directed to the exhaust fluid passageway 40.

A pilot valve assembly, indicated generally by the reference numeral 150, is reciprocally disposed in a pilot valve cavity in the motor piston body 30, the pilot valve cavity being indicated generally by the reference numeral 152. The pilot valve cavity 152 is comprised of a small diameter portion 154 and a large diameter portion 156 and is closed at the top thereof by the insert member 32. The small diameter portion 154 may be formed by a downwardly directed bore and is in iiuid communication with the interior of the cylinder sleeve 26 below the piston member 22. The lower end of the bore forms a shoulder 158 for arresting the downward travel of a lower pilot valve member, presently to be described. A control port 160 provides fluid communication between the annular control chamber 116 and the portion 156 of the pilot valve cavity 152. A pair of low pressure exhaust ports 162 and 164 are in fluid communication with the portion 156 of the pilot valve cavity 152, substantially as shown in FlG. l. The exhaust port 162 communicates with an annular passageway 166 formed between the walls of the bore 94 and the portion 106 of the main valve 98. The exhaust port 164 is in direct communication with the bore 94. Both of the exhaust ports 162 and 164 are therefore in fluid communication with the exhaust fluid passageway 40 through the passageway 96 and the bores 100 and 102.

A high pressure power fluid port 170, shown only in FIG. 5, comprises a bore 171 and an annular groove 172 in the wall of the pilot valve cavity 152. The power fluid port provides uid communication between one of the power fluid bores 130 and the larger portion 156 of the pilot valve cavity 152 at a position substantially along the lines 5 5 of FIG. l. The power iluid port 170 is also illustrated in the schematic view of FIG. 7 by dotted outline, and in FIGS. 9, l() and 1l. Another power fluid port, indicated generally by the reference numeral 174, provides fluid communication between the power uid in bore 130 and the pilot valve cavity. The power uid port 174 may be traced by combined reference to FIGS. 1 and 6 and is comprised of a passageway 176 in the motor piston body 30 `which communicates with one of the bores 130, a tubular sleeve 178, a passageway in the insert member 32, an inner annular groove 182 in the upper face of the insert member 32, a ball valve cavity 184 in the retainer plug 34, a passageway 186 in the retainer plug 34, an outer annular groove 187 in the insert member 32, and a passageway 188 in the insert 32 which communicates with the upper end of the pilot valve cavity 152. The sleeve 178 provides a means for assuring alignment between the passageways 176 and 180, and the inner and outer annular grooves 182 and 187 eliminate the necessity of aligning the ball valve cavity 184 with the passageway 180 and the passageway 186 with the passageway 188. A ball valve 190 is disposed in the ball valve cavity 184 and is adapted to mate with a downwardly facing seat formed in the retainer plug 34 so as to normally check the passage of high pressure fluid through the power fluid port 174 from the bore 130 to the pilot valve cavity 152. A striker pin 192 is reciprocally dis- 122 and the radial posed in a bore in the retainer plug 34. The striker pin 192 extends above the retainer plug 34 and upon striking the lower end 194 of the upper packing housing 24,

loves downwardly to unseat the ball valve 190 and permit high pressure power fluid to pass through the power fluid port 174 into the upper end of the pilot valve cavity 152.

A lower pilot valve member 200 is disposed in the portion 154 of the pilot valve cavity 152 and is of such a diameter as to provide a peripheral fluid seal with the fluid motor piston body 30. When the lower pilot valve member 200 is in the lower position and resting on the shoulder 158, substantially as shown in FIGS. 1 and 7, the lower end of the member 200 will strike the upper face 202 of the lower packing housing 28 as the piston member 22 approaches its lower limit of travel, and will be moved upwardly to effect a shift of the pilot valve assembly and a reversal of the travel of the piston member 22, as will hereafter be described in greater detail.

An upper pilot valve member 204 is disposed in the larger portion 156 of the pilot valve cavity 152. The upper pilot valve member 204 is so sized as to provide a peripheral lluidtight seal with the portion 156 of the pilot valve cavity 152. A first annular groove 206 is of sufllcient length as to place the control port 160 in fluid communication with the exhaust fluid port 162, or alternatively in fluid communication with the annular power fluid port 172. A second annular groove 208 is placed in continuous iluid communication with the'exhaust pressure port 164 by a passageway 210 which extends through the body of the upper pilot valve member 204. When the pilot valve assembly is in the lower position, as shown in FIG. l, fluid communication is provided between the high pressure fluid in the high pressure port 170 and the pilot valve cavity 152 above the upper pilot valve member 204 by a fluid passageway 212 and an annular groove 214 as can best be seen in FIGS. 9, l and 11. The upper end of the pilot valve cavity 152 is enlarged at 216 a few thousandths of an inch to provide a highly restrictive annular passageway 218 around the upper pilot valve member 204, in order to provide fluid communication between the annular groove 208 and the pilot valve cavity 152 above the upper valve member 264 when the pilot valve assembly is in the up position shown in FIGS. 9 and l0. T he highly restrictive annular passageway 218 causes a sufllcient pressure drop thereacross to effect a shift of the pilot valve assembly as hereafter described.

Operation The pumping unit 1S is installed in operative position in a wellbore by connecting a relatively large tubing string to the upper packing housing 24 by the threaded coupling 220, and a relatively shall tubing string to the internally threaded bore 124 of the lower packing housing 28. A seating nipple (not shown) may be connected to the standing valve assembly 66 by the threaded coupling 222. The pumping unit can then be lowered into a wellbore by the tubing strings until the seating nipple is seated in a conventional shoe disposed at the producing formation. Hydraulic power fluid may then be pumped downwardly through the smaller tubing string into the bore 124 and through the passageway means 126 and 128 into the interior of the motor cylinder below the piston member 22. Hydraulic power fluid will also enter the bores 130 and pass upwardly to the annular passageway 132 of the main valve cavity. Assume now that gravity has caused the piston members 22 and 60 to be in the lowcrmost position, and the main valve 98 to be in the lower position shown in FIG. 1. The lower pilot valve member 230 will accordingly be in contact with the upper surface 202 of the lower packing housing 28 so as to be slightly raised substantially to the position shown in FIG. 9. High pressure power fluid below the motor piston 22 will act on the lower end of the lower pilot valve member 2553. The upper end of the lower pilot valve member 200 and the lower end of the upper pilot valve iember 204 are always exposed to exhaust pressure through the exhaust fluid port 164. The upper end of the upper pilot valve member 204 is also in fluid communication with the exhaust fluid port 164 through the annular passageway 218, the annular groove 208, and the passageway 210. Therefore, even though the area or the upper end of the upper pilot valve member 204 is greater than the area of the lower end of the lower pilot valve member 200, the high pressure fluid acting on the lower end of the lower pilot valve member 200 is suflicient to shift the entire pilot valve assembly 150 upwardly to the up position shown in FIG. 10. It will be noted that high pressure power fluid passing from the bore 130 through the high pressure power fluid 174 and then through the annular passageway 218 onto the exhaust passageway 154 will seat the ball valve 190 to insure that the pressure on the upper end of the upper pilot valve member 204 will be maintained at low exhaust pressure by communication with the exhaust port 164 as described. It will also be noted that when the pilot valve assembly is in the position shown in FIG. 9, the high pressure power fluid port 170 is placed in fluid communication with the control port 160 by the annular groove 206. Therefore, high pressure power fluid will be introduced to the control chamber 116 and acts on the control surface 114 of the main valve member 98, and the main valve member 98 will be shifted upwardly to the upper position shown in FIG. 8.

When the main valve member 98 is in the upper position, the power fluid annular passageway 132 is closed and the annular passageway 122 registers with the annular passageway 134. Fluid communication is then established between the exhaust port 40 and the interior of the cylinder sleeve 26 above the piston member 22 by the passageway means comprised of the annular passageway 138, the bores 136, the registering annular passageways 134 and 122, and the bores 120. Any fluid which may be within the cylinder sleeve 26 above the piston member 22 is vented to the exhaust port 40. The high pressure power fluid below the piston member 22 will then move the piston member 22 and therefore the pump piston member 60 through an upstroke.

Assuming that the pump piston member 60 was in its lowermost position when operation of the pumping unit was started, well fluids will have entered through the passageway 72, passed upwardly through the upwardly opening standing valve 66, through the passageway 84 and by the upwardly opening traveling valve 88. Some well fluids will also have passed through the passageways 56 into the interior of the pump cylinder sleeve 62 above the pump piston member 60. Ot course, well fluids will also have entered into the passageway 50 of the tubular connecting rod 48, to some height, depending upon the pressure of the well fluids. Then as the pump piston member 60 moves through an upstroke, the downwardly closing traveling valve 88 will close, and all well fluids above the piston member 60 will pass through the passageways 86 into the pump fluid passageway 50, and then upwardly through the passageways 94, 96, and 102 to the exhaust fluid port 40. As previously mentioned, any fluid within the motor cylinder sleeve 26 above the motor piston 22 will also be displaced into the interior passageway 96 of the valve member 98 and mingle with the well fluids from the well fluid passageway 50 before entering the exhaust port 40. The combined fluids will then pass upwardly through the tubing string connected to the pump unit 15 by the threaded coupling 220 to the wellhead.

As the motor piston 22 approaches the upper limit of its travel, the striker pin 192 will contact the lower face 194 of the upper packing housing 24 and will move downwardly to unseat the ball valve 190. High pressure fluid from the bore will then pass through the high pressure port 174 to the upper end of the pilot valve cavity 152 above the upper end of the upper pilot valve member 204. Since the cross sectional area of the annular passageway 218 is sufficiently small as to cause a substantial pressure drop thereacross, the pressure on the upper end of the upper pilot valve member 204 will be approximately equal to that of the high pressure power fluid. Therefore, as the striker pin 192 holds the ball valve 190 open, the high pressure power fluid acting on the larger area of the upper pilot valve member 204 will overcome the force of the same high pressure power lluid acting on the smaller arca of the lower end of the lower pilot valve member 200, and the entire pilot valve assembly 150 will be shifted downwardly.

As soon as the pilot valve assembly 150 has traveled downwardly to the position shown in FIG. ll, the annular groove 208 will be closed and the annular groove 214 will register with the high pressure power fluid port 170. High pressure power fluid will then pass from the bore 130 through the high pressure port 170 to the annular groove 214 and through the passageway 212 to the pilot valve cavity 152 above the upper end of the upper pilot valve member 204. The pilot valve assembly 150 will then be shifted completely to its lowermost position as shown in FlGS. l and 7. The high pressure in the control chamber 116 will then be vented to exhaust pressure by the annular groove 206, which places the control passageway 160 in fluid communication with the exhaust port 162. The main valve member 98 will then be shifted downwardly to the lower position shown in FIGS. l and 7. High pressure power fluid in the pilot valve cavity 152 above the upper pilot valve member 204 from the high pressure port 170 will maintain the pilot valve assembly shifted downwardly until it is mechanically moved upwardly at the bottom of the downstroke as hereafter described in greater detail.

When the main valve member 98 is shifted downwardly to the lower position shown in FIGS. l and 7, the high pressure power fluid in the annular passageway 132 passes through the annular groove 112 in the main valve member 98 to the annular passageway 134, and then through the radial apertures 136 and the annular passageway 138 to the interior of the cylinder sleeve 26 above the piston member 22. High pressure power fluid will then be both above and below the motor piston member 22. However, since the cross sectional area of the connecting rod 4S is greater than the cross sectional area of the piston rod 38, the effective hydraulic working area of the upper face of the motor piston member 22 will be greater than the effective hydraulic working area of the lower face, and the net hydraulic force will move the piston member 22 and the pump piston member 60 through a downstroke.

As the pump piston member 60 moves downwardly, the downwardly closing standing valve 74 will close and the well fluids in the pump cylinder sleeve 62 below the pump piston member 60 will force the traveling valve 8S open and will pass upwardly through the passageway means 84. The major portion of the well fluid passing through the passageway means 84 will pass through the passageways 86 to the interior of the pump cylinder sleeve 62 above the pump piston member 60. However, a portion of the well fluid equal to the volume of the connecting rod 48 which is within the pump cylinder member 58 will be displaced and passed upwardly through the well fluid passageway 50. It will be appreciated that the quantity of fluid pumped by displacement during the downstroke is at a minimum and therefore the power demand from the uid motor 16 is relatively small. Accordingly, the difference in cross sectional area between ythe connecting rod 48 and the piston 38 may be relatively. small so that the fluid passageways 50 and 40 may be made substantially equal in cross sectional area.

As the motor piston member 22 approaches the end of the downstroke, the lower end of the lower pilot valve member 200 will strike the upper face 202 of the lower 'shown in FIG. 9.

packing housing 28 and the entire pilot valve assembly will be mechanically shifted upwardly to the position When the pilot valve assembly reaches the position shown in FIG. 9, the high pressure power fluid in the pilot valve cavity above the upper pilot valve member 204 will be vented to exhaust through the passageway means comprised of the annular passageway 218, the annular groove 208, the passageway 210, the pilot valve cavity 152 between the pilot valve members 200 and 204, and the exhaust port 164. At the same time, the annular groove 214 will have moved sufficiently to close the high pressure power uid port 170. Power fluid passing through the high pressure port 174 will seat the ball valve 190 to close the port 174. Additional high pressure power fluid cannot then be introduced to the pilot valve cavity 152 above the upper pilot valve member 204. Since the fluid acting on the upper end of the upper pilot valve member 204 is at low exhaust pressure, and high pressure power fluid is acting on the lower end of the lower pilot valve member 200, the entire pilot valve assembly 150 will be shifted to the upper position shown in FIG. l0.

As soon as the pilot Valve assembly 150 was partially shifted upwardly to the position shown in FIG. 9, the annular passageway 206 places the high pressure power lluid in the high pressure port 170 in communication with the control fluid port and therefore with the control fluid cavity 116. The high pressure power fluid entering the control cavity 116 will act on the control working surface 114 and will shift the main valve member i8 upwardly to the upper position shown in FIG. S. As previously described, when the main valve member 98 is in the up position, the piston members 22 and 60 will travel through an upstroke, and the well fluids in the pump cylinder sleeve 62 above the pump piston member 60, together with the exhaust fluid from the interior of the motor cylinder sleeve 26 above the motor piston member 22, will pass upwardly through the exhaust port 40. Thus sequence of events will then continue indefinitely so long as power fluid is supplied through the bore 124 of the lower packing housing 2S, and the well fluids will accordingly be pumped to the wellhead.

Although the particular embodiment of the present invention herein described and illustrated is of the reverse flow, insert type wherein the pumping unit 15 is inserted into the wellbore by two separate tubing strings, it will readily be evident to those skilled in the art that the novel pump construction is particularly well adapted for use in a reverse ow, free type pump cavity as described and claimed in US. Patent No. 2,988,005. In such a construction, the power fluid can be pumped down the smaller diameter tubing string to the pump cavity and introduced to the lower packing assembly 28. A suitable annular packer would then be placed above the inlet to ,the lower packing assembly and within the annulus between the external diameter of the pumping unit and the larger diameter tubing string in which the pumping unit is disposed. Since the well fluids pumped by the pump unit and the exhaust fluid from the motor are both directed upwardly through the motor piston member 22, the external diameter of the motor cylinder member 20 could correspond approximately to the internal diameter of the larger tubing string in which the pumping unit would be located. Since the main valve member 98 is tubular and is disposed in the well and exhaust fluid passageway means, the passageway means may be increased to a maximum to thereby decrease the pressure drop of the well fluids passing through the motor piston member 22. Also, it will be evident to those skilled in the art that a highly useful and novel pilot valve assembly has been described for shifting the sleeve type main valve member 98 which is of very simple and economical construction and foolproof in operation.

Having thus described the preferred embodiment of the invention and the subcombinations thereof, it is to be understood that various changes and substitutions can be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

What is claimed is:

1. A subsurface pumping unit comprising:

a motor cylinder member;

a motor piston member reeiprocally disposed in the motor cylinder member;

a pump comprising a pump cylinder member connected to the motor cylinder member and a pump piston member reeiprocally disposed in the pump cylinder member,

a connecting rod member connected to the motor piston member, the connecting rod member extending through one end of the motor cylinder member and through one end of the pump cylinder member and being connected to the pump piston member,

a second rod member connected to the motor piston member and extending through the other end of the motor cylinder member;

valving means having a main valve member disposed in the motor piston member for applying high pressure power fluid to the interior of the motor cylinder member for reciprocating the piston members, and

fluid passageway means through the connecting rod member, through the motor piston member and main valve member, and through the second rod member for passing well fluids pumped by the pump upwardly therethrough, whereby maximum utilization of the cross sectional area of the pumping unit can be attained.

2. A subsurface pumping unit comprising:

a motor cylinder member;

a motor piston member reeiprocally disposed in the motor cylinder member;

the motor piston member having a first working area facing one end of the motor cylinder member and a second working area facing the opposite end of the motor cylinder member, the first working area being smaller than the second working area;

a pump cylinder member connected to the motor cylinder member;

a pump piston member reeiprocally disposed in the pump cylinder member and having an upper face;

a connecting rod member connected to the motor piston member, the connecting rod member extending through one end of the motor cylinder member and through one end of the pump cylinder member and being connected to the pump piston member;

a second rod member extending through the other end of the motor cylinder member;

a downwardly closing standing valve assembly disposed in the other end of the pump cylinder member;

first well fluid passageway means through the pump piston member;

a downwardly closing traveling valve assembly disposed in the first well fluid passageway means for checking the downward passage of fluid therethrough;

a second well fluid passageway means in fluid communication with the upper face of the pump piston member and extending through the connecting rod member, through the motor piston member, and through the second rod member;

power fluid passageway means in the motor cylinder member for providing fluid communication between a source of power fluid and the first working area of the motor piston member;

a main valve cavity in the motor piston member, the valve cavity being intersected by the second well fluid passageway means;

third fluid passageway means in the motor piston member for providing fluid communication between the first working area and the main valve cavity;

fourth fluid passageway means in the motor piston member for providing fluid communication between the second working area and the main valve cavity;

fifth fluid passageway means in the motor piston member for providing fluid communication between the main valve cavity and the second well fluid passageway means; and,

main valve means positioned in the main valve cavity and operatively connected to the motor piston member for placing the fourth fluid passageway means in fluid communication with the fifth fluid passageway means and closing the third fluid passageway means, and alternatively, upon shifting of the valve means, for placing the third fluid passageway means in fluid communication with the fourth fluid passageway means and closing the fifth fluid passageway means, the main valve member having a bore therethrough forming a part of the second well fluid passageway means,

whereby the piston members will be reciprocated upon shifting of the main valve means.

3. A subsurface pumping unit comprising:

a motor cylinder member;

a motor piston member reeiprocally disposed in the motor cylinder member;

the motor piston member having a first working area facing one end of the motor cylinder member and a second working area facing thc opposite end of the motor cylinder member, the first working area being smaller' than the second working area;

a pump cylinder member connected to the motor cylinder member;

a pump piston member reeiprocally disposed in the pump cylinder member and having an upper face;

a connecting rod member connected to the motor piston member, the connecting rod member extending through one end of the motor cylinder member and through one end of the pump cylinder member and being connected to the pump piston member;

a second rod member extending through the other end of the motor cylinder member;

a downwardly closing standing valve assembly disposed in the other end of the pump cylinder member;

a first well fluid passageway means through the pump piston member;

a downwardly closing traveling valve assembly disposed in the first well fluid passageway means for checking the downward passage of fluid therethrough;

a second well fluid passageway means in fluid communication with the upper face of the pump piston member and extending through the connecting rod member, through the motor piston member, and through the second rod member;

power fluid passageway means in the motor cylinder member for providing fluid communication between a source of power fluid and the first working area of the motor piston member;

a main valve cavity in the motor piston member;

third fluid passageway means in the motor piston member for providing fluid communication between the first working area and the main valve cavity;

fourth fluid passageway means in the motor piston member for providing fluid communication between the second working area and the main valve cavity;

fifth fluid passageway means in the motor piston member for providing fluid communication between the main valve cavity and the second well fluid passageway means; and,

main valve means positioned in the main valve cavity and operatively connected to the motor piston member for placing the fourth fluid passageway means in fluid communication with the fifth fluid passageway means and closing the third fluid passageway means, and alternatively, upon shifting of the valve means, for placing the third fluid passageway means in fluid communication with the fourth fluid passageway means and closing the fifth fluid passageway means, the main valve means comprising a hydraulically shifted, differential area main valve member having a control working area thereon, the valve member being shifted to one position when a high pressure fluid is applied to the control working area and shifted to the other position when low pressure fluid is applied to the control working area, and pilot valve means for controlling the application of high and low pressure fluid to the control working area,

whereby the piston members will be reciprocated upon shifting of the main valve means.

4. A subsurface pumping unit as defined in claim 3 wherein the pilot valve means is comprised of:

a pilot valve cavity -in the motor piston member;

a control passageway means for providing fluid communication between the pilot valve cavity and the control working area on the main valve member,

a first high pressure pilot passageway means for providing fluid communication between a source of high pressure power fluid and the pilot valve cavity,

a first low pressure pilot passageway means for providing fluid communication between the pilot valve cavity and the second well fluid passageway means; and,

a pilot valve member positioned in the pilot valve cavity and operatively connected to the motor piston member for placing the high pressure pilot passageway means in fluid communication with the control passageway means and closing the low pressure pilot passageway means when in one position, and alternatively, upon shifting of the pilot valve means to another position, for placing the low pressure pilot passageway means in fluid communication with the control passageway means and closing the high pressure pilot passageway means.

5. A subsurface pumping unit as defined in claim 4 wherein:

the pilot valve member is further characterized as a differential area member having large and small hydraulic working areas at opposite ends thereof; and,

the pilot valve means is further characterized by,

second high pressure pilot passageway means for providing fluid communication between a source of high pressure power fluid and the small hydraulic working area,

third high pressure pilot passageway means for providing fluid communication between a source of high pressure power fluid and the large hydraulic working area, and

a third valve means positioned in the third high pressure pilot passageway means for controlling the passage of high pressure fluid therethrough to the large hydraulic working area,

fourth high pressure pilot passageway means for providing fluid communication between a source of high pressure fluid and the large hydraulic working area, the fourth high pressure pilot passageway means being closed when the pilot valve member is shifted to the said one position and open when the pilot valve member is shifted to the said other position,

a second low pressure pilot passageway means for providing fluid communication between the large hydraulic working area and the second well fluid passageway means, the second low pressure pilot passageway means being closed when the pilot valve member is in said other position,

first mechanical means for opening the third valve means as the motor piston member approaches one end of the motor cylinder member, and

second mechanical means for shifting the pilot valve member to close the fourth high pressure pilot passageway means as the motor piston member ap- 14 proaches the other end of the motor cylinder member.

6. A subsurface pumping unit as defined in claim 5 wherein:

the pilot valve cavity is formed by a bore and a larger counterbore in the motor piston member, and

the pilot valve member is comprised of a first member reciprocally disposed in the bore and a second member reciprocally disposed in the counterbore.

7. A subsurface pumping unit as defined in claim 6 wherein:

the second high pressure. pilot passageway means is formed by the bore of the pilot valve cavity, and

the second mechanical means is comprised of the end of the end of the second member projecting through the bore.

8. A pilot valve means for controlling the application of high and low pressure fluid to the control working surface of a differential area main valve disposed in the piston member of a fluid motor, the piston member being reciprocally disposed in a cylinder member having two ends, the pilot valve means comprising:

a pilot valve cavity in the piston member;

control fluid passageway means for providing fluid communication between the control working surface of the main valve and the pilot valve cavity;

first high pressure fluid passageway means for providing fluid communication between the control working surface of the main valve and a source of high pressure fluid;

first low pressure fluid passageway means for providing fluid communication between the pilot valve cavity and a low pressure passageway;

a pilot valve member disposed in the pilot valve cavity and operatively connected to the motor piston member for, when in one position, placing the first high pressure fluid passage means in fluid communication with the control fluid passageway means and for closing the first low pressure fluid passageway means, and alternatively, when in another position for placing the rst low pressure fluid passageway means in fluid communication with the control fluid passageway means and for closing the first high pressure fluid passageway,

the pilot valve member having a large hydraulic working area opposing a small hydraulic working area;

a second high pressure fluid passageway means for providing fluid communication between the large hydraulic working area and a source of high pressure fluid;

a check valve means disposed in the second high pressure fluid passageway means for checking the flow of fluid to the large hydraulic working area;

mechanical means for opening the check valve means as the motor piston approaches one end of the cylinder member;

a third high pressure fluid passageway means for providing fluid communication between the small hydraulic working area and a source of high pressure fluid;

a fourth high pressure fluid passageway means for providing fluid communication between the large hydraulic working area and a source of high pressure fluid,

the fourth high pressure fluid passageway means being closed by the pilot valve member when the pilot valve member is shifted toward the large hydraulic working area and open when the pilot valve member is shifted toward the small hydraulic working area;

a second low pressure fluid passageway means for providing fluid communication between the large hydraulic working area and a low pressure fluid passageway,

the second low pressure fluid passageway means being closed by the pivot valve member when the pilot valve member is shifted toward the small hydraulic working area and being open when the pilot valve member is shifted toward the large hydraulic working area; and

mechanical means for shifting the pilot valve member for opening the second low pressure fluid passageway means as the piston member approaches the other end of the cylinder member.

9. A pilot valve means as dened in claim 8 wherein:

the pilot valve cavity is formed by a bore in the piston member and a larger counterbore in the piston member, and

the pilot valve member is comprised of two separate parts, one disposed in the bore and one disposed in the counterbore.

References Cited in the file of this patent UNITED STATES PATENTS FOREIGN PATENTS Germany Jan. 4, 1901 

1. A SUBSURFACE PUMPING UNIT COMPRISING: A MOTOR CYLINDER MEMBER; A MOTOR PISTON MEMBER RECIPROCALLY DISPOSED IN THE MOTOR CYLINDER MEMBER; A PUMP COMPRISING A PUMP CYLINDER MEMBER CONNECTED TO THE MOTOR CYLINDER MEMBER AND A PUMP PISTON MEMBER RECIPROCALLY DISPOSED IN THE PUMP CYLINDER MEMBER; A CONNECTING ROD MEMBER CONNECTED TO THE MOTOR PISTON MEMBER, THE CONNECTING ROD MEMBER EXTENDING THROUGH ONE END OF THE MOTOR CYLINDER MEMBER AND THROUGH ONE END OF THE PUMP CYLINDER MEMBER AND BEING CONNECTED TO THE PUMP PISTON MEMBER; A SECOND ROD MEMBER CONNECTED TO THE MOTOR PISTON MEMBER AND EXTENDING THROUGH THE OTHER END OF THE MOTOR CYLINDER MEMBER; VALVING MEANS HAVING A MAIN VALVE MEMBER DISPOSED IN THE MOTOR PISTON MEMBER FOR APPLYING HIGH PRESSURE POWER FLUID TO THE INTERIOR OF THE MOTOR CYLINDER MEMBER FOR RECIPROCATING THE PISTON MEMBERS, AND FLUID PASSAGEWAY MEANS THROUGH THE CONNECTING ROD MEMBER, THROUGH THE MOTOR PISTON MEMBER AND MAIN VALVE MEMBER, AND THROUGH THE SECOND ROD MEMBER FOR PASSING WELL FLUIDS PUMPED BY THE PUMP UPWARDLY THERETHROUGH, WHEREBY MAXIMUM UTILIZATION OF THE CROSS SECTIONAL AREA OF THE PUMPING UNIT CAN BE ATTAINED. 